Coolant leak - pressure test

[SzymekCRX]

Hello everyone,

after coming back to my garage one day with my C5 I've noticed some fluid underneath - it was the coolant fluid.

This was only one time when I found some spillage so I decided to do some pressure tests.

I managed to modify the coolant tank cap and add the hose to it. I pressurised it to around 10 PSI.

No leaks. It hold the pressure without any problem.

It was done on the stationary, cooled engine. Is there any difference within the cooling water circuit when the thermostat is open ? Should I try to perform pressure test on the warm engine ?

PS.
Water pump leak - occurs on the running engine rarely?

[lswing]

I just fixed up my coolant leak, both of the aux radiators behind the IC's, take a look down there. Drivers side was super corroded, other a bit, both leaking...

[ThrillHouse]

My slow coolant leak is going to be fixed tomorrow. The After Run pump took a dump (verified via a boroscope). Its under the intake manifold. Instead of a 'normal' R&R I am relocating the pump itself

[kismetcapitan]

I have a slow leak in a valve that only opens during the after run cooldown, so it won't show up in a pressure test. I'll get around to replacing it, but for now, I just have to add maybe half a liter of coolant every month or so. It's this plastic thing that's easily seen/accessed when you pull the bottom engine cover off.

[marklar182]

Check the coolant valve that sits above where the PS hoses connect to the cooler hard lines.

[SzymekCRX]

I have a slow leak in a valve that only opens during the after run cooldown, so it won't show up in a pressure test. I'll get around to replacing it, but for now, I just have to add maybe half a liter of coolant every month or so. It's this plastic thing that's easily seen/accessed when you pull the bottom engine cover off.

This one ?

[SzymekCRX]

Check the coolant valve that sits above where the PS hoses connect to the cooler hard lines.

That one ?

[kismetcapitan]

This one ?

yep, that solenoid valve. the second pic shows what looks like a passive checkvalve. I'm tempted to seal that solenoid valve with a generous helping of silicone sealant; the leak is so slow that five bucks of sealant could hold that valve for a year. It's christmas time, and discretionary funds have been going in a myriad directions

[lswing]

I've got those hoses, tubes and such...just in a box now

[SteveKen]

It could be the coolant after run pump?

Also, don't forget about the pipe running from the engine block to the oil cooler.

[SzymekCRX]

Hello. My pressure test did a good job overnight. I found a pile of coolant underneath my RS6.

It is dripping from underneath the engine. Droplets are forming on the edge of the oil sump. Can it be the water pump ? The hoses above look clean.

Yes I know it's dirty. Mainly because of faulty valce covers till now.

[Jimmy Joe]

I had a leak caused by the metal strap that runs in front of the big radiator fan rubbing against it, a pin hole leak that the radiator shop fixed for sixty bucks, cleaning service and repaint included. That lead to the discovery that the solenoid valve had shorted by coolant getting to the electrical conections. A $ 100 dlls. piece. The rubbing of the metal strap can be prevented by using a bycycle tire inner tube ribbon glued to it. Fortunately, the Modine radiator is still fabricated the old fashion way, that is, cooper fins instead of those flimsy plastic/ aluminium contraptions sold nowdays. ¿ Cost of replacement at Audi? $ 1, 384.60 dlls. You install it.

[SzymekCRX]

I still suffer this leak somewhere.. I find a pond of coolant under my car in my garage everytime I come back to my car after doing some driving.

It only leaks when the pressure inside the cooling system builds up.

Is it possible that pressure regulating valve is faulty and it doesn't relief the pressure ? Where is it located ?

Normally it should be located at the of of the radiator. Where is it located in our RS6s ?

It should look like this:

[MaxRS6]

Have you checked the oil cooler? Hopefully- it is something else..

[SzymekCRX]

Have you checked the oil cooler? Hopefully- it is something else..

Oil cooler how ? I'm loosing the engine coolant not the oil

Edit:

I know what You mean now:

http://www.justanswer.com/audi/1w7rt...ows-floor.html

You may be absolutely right - the symptoms are the same (looking at my photo) - the passenger side

[hahnmgh63]

Since it looks like it is dripping on the right side of the engine it could be a number of things. Some easy and at least one not so much (Oil cooler). Both Radiator hoses (upper & lower connect on the right side of the radiator, snap on fittings with an internal O-ring. There is a coolant hose elbow that goes to the Thermostat inlet pipe at the front right of the engine just below the valve cover you should see. The difficult one is the Oil Cooler that is below all of that behind the right side motor mount. There is a short 2" plastic Coolant pipe that connects the oil cooler to the block and it has been known to get brittle and crack with age & heat. This pipe is commone on most of the 4.2 V8's. There is a guy (Bufkin Engineering) that makes a beautiful replacement piece out of aluminum and as a Bonus he has a double O-ring seal on his piece so it should last the life of the car, and he only charges about $25 for the piece. While my engine was out I installed one since it was easy to access, Speedtrapped sold me one that he bought but his mechanic forgot to install it. If it is the Oil cooler pipe you can probably lower the engine cradle a few inches to get at it but I'm sure Audi lists it as an Engine pull.

P.S. The RS6 has the finned Air to Oil Combination Engine/Transmission oil cooler in front of the radiator and the small finned Coolant to Oil heat exchanger on the right lower side of the engine block (helps warm the oil when cold and cool it when it's hot).

[MaxRS6]

Here was my oil cooler tube repair journey

http://www.rs6.com/showthread.php/20...oo!?highlight=

[SzymekCRX]

Cool ! This can be done as DIY w/o engine pull, right ?